Sensing a phase-path current in a coupled-inductor power supply

ABSTRACT

An embodiment of a power supply includes an output node, inductively coupled phase paths, and a sensor circuit. The output node is configured to provide a regulated output signal, and the inductively coupled phase paths are each configured to provide a respective phase current to the output node. And the sensor circuit is configured to generate a sense signal that represents the phase current flowing through one of the phase paths. For example, because the phase paths are inductively coupled to one another, the sensor circuit takes into account the portions of the phase currents induced by the inductive couplings to generate a sense signal that more accurately represents the phase current through a single phase path as compared to conventional sensor circuits.

CLAIM OF PRIORITY

The present application is a Continuation of copending U.S. patentapplication Ser. No. 12/189,112, filed 8 Aug. 2008; which applicationclaims priority to U.S. Provisional Application Ser. Nos. 60/964,792filed on Aug. 14, 2007, now expired, and U.S. Provisional ApplicationSer. Nos. 61/072,287 filed on Mar. 27, 2008, now expired; all of theforegoing applications are incorporated herein by reference in theirentireties.

SUMMARY

An embodiment of a power supply includes an output node, inductivelycoupled phase paths, and a sensor circuit. The output node is configuredto provide a regulated output signal, and the inductively coupled phasepaths are each configured to provide a respective phase current to theoutput node. And the sensor circuit is configured to generate a sensesignal that represents the phase current flowing through one of thephase paths.

For example, because the phase paths are inductively coupled to oneanother, the sensor circuit takes into account the portions of the phasecurrents induced by the inductive couplings to generate a sense signalthat more accurately represents the phase current through a single phasepath as compared to conventional sensor circuits. The sense signal maybe fed back to a power-supply controller, which regulates the outputsignal (e.g., an output voltage) at least partly in response to thefed-back sense signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an embodiment of a coupled-inductormultiphase power supply that includes sense circuits for sensing thephase currents.

FIG. 2 is a schematic diagram of a portion of the power supply of FIG. 1including the phase-path windings, and an embodiment of the sensorcircuits of FIG. 1.

FIG. 3 is a schematic diagram of a two-phase version of the power-supplyportion of FIG. 2.

FIGS. 4A and 4C are timing diagrams of sense signals that are generatedby the sensor circuits of FIG. 3.

FIGS. 4B and 4D are timing diagrams of the phase currents flowingthrough the windings of FIG. 3.

FIG. 5 is a schematic diagram of a portion of a two phase version of thepowers supply of FIG. 1 including the phase-path windings and anotherembodiment of the sensor circuits of FIG. 1.

FIG. 6 is a block diagram of an embodiment of a computer system having apower supply that includes sensor circuits that are the same as orsimilar to one or more of the embodiments discussed above in conjunctionwith FIGS. 2-3 and 5.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of an embodiment of a coupled-inductor(CI) multiphase power supply 10, here a CI buck converter, whichprovides a regulated output voltage V_(out) at a supply output node 11,and which includes phase paths (alternatively “phases”) 12 ₁-12 _(n) andcurrent sensors 14 ₁-14 _(n) for respectively sensing the currentsi₁-i_(n) through the phases. As discussed below in conjunction withFIGS. 2-5, the current sensors 14 ₁-14 _(n) may each be coupled torespective multiple phase paths 12 ₁-12 _(n) at nodes or locations otherthan the supply output node 11. For example, assume that some or all ofthe phases 12 ₁-12 _(n) are magnetically coupled to one another.Coupling a current sensor 14 not only to a first phase 12 for which thesensor measures the phase current, but also to one or more second phases12 to which the first phase is magnetically coupled, may allow thesensor to sense the current through the first phase more accurately thansome conventional current sensors can.

The current sensors 14 ₁-14 _(n) respectively generate sense signalsI_(FB1)-I_(FBn), which respectively represent the phase currentsi₁-i_(n). For example, each of the signals I_(FB1)-I_(FBn) may be arespective voltage that has substantially the same signal phase as thecorresponding phase current i and that has an amplitude that issubstantially proportional to the amplitude of the corresponding phasecurrent.

In addition to the current sensors 14 ₁-14 _(n), the converter 10includes a coupled-inductor assembly 16 having windings 18 ₁-18 _(n),which are wound about a common core (not shown in FIG. 1) and which aremagnetically coupled to one another via the core, a power-supplycontroller 20, high-side drive transistors 22 ₁-22 _(n), low-side drivetransistors 24 ₁-24 _(n), a filter capacitor 26, and an optional filterinductor 28. A winding 18 and the high-side and low-side transistors 22and 24 coupled to the winding at a phase intermediate node INT compose arespective phase 12. For example, the winding 18 ₁ and the transistors22 ₁ and 24 ₁ compose the phase 12 ₁.

The controller 20 may be any type of controller suitable for use in amultiphase CI power supply, is supplied by voltages VDD_(controller) andVSS_(controller), and receives the regulated output voltage V_(out), areference voltage V_(ref), and the sense signals I_(FB1)-I_(FBn), whichare fed back to the controller from the current sensors 14 ₁-14 _(n),respectively. The controller 20 may use V_(ref) and the fed back V_(ont)and I_(FB1)-I_(FBn) to conventionally regulate V_(out) to a desiredvalue.

The high-side transistors 22 ₁-22 _(n), which are each switched “on” and“off” by the controller 20, are power NMOS transistors that arerespectively coupled between input voltages VIN₁-VIN_(n) and the nodesINT₁-INT_(n). Alternatively, the transistors 22 ₁-22 _(n) may be otherthan power NMOS transistors, and may be coupled to a common inputvoltage. Moreover, the transistors 22 ₁-22 _(n) may be integrated on thesame die as the controller 20, may be integrated on a same die that isseparate from the die on which the controller is integrated, or may bediscrete components.

Similarly, the low-side transistors 24 ₁-24 _(n), which are eachswitched on and off by the controller 20, are power NMOS transistorsthat are respectively coupled between low-side voltages VL₁-VL_(n) andthe nodes INT₁-INT_(n) of the phase windings 18 ₁-18 _(n).Alternatively, the transistors 24 ₁-24 _(n) may be other than power NMOStransistors, and may be coupled to a common low-side voltage such asground. Moreover, the transistors 24 ₁-24 _(n) may be integrated on thesame die as the controller 20, may be integrated on a same die that isseparate from the die on which the controller is integrated, may beintegrated on a same die as the high-side transistors 22 ₁-22 _(n), maybe integrated on respective dies with the corresponding high-sidetransistors 22 ₁-22 _(n) (e.g., transistors 22 ₁ and 24 ₁ on a firstdie, transistors 22 ₂ and 24 ₂ on a second die, and so on), or may bediscrete components.

The filter capacitor 26 is coupled between the regulated output voltageV_(out) and a voltage VSS_(cap), and works in concert with the windings18 ₁-18 _(n) and an optional filter inductor 28 (if present) to maintainthe amplitude of the steady-state ripple-voltage component of V_(out)within a desired range which may be on the order of hundreds ofmicrovolts (μV) to tens of millivolts (mV). Although only one filtercapacitor 26 is shown, the converter 10 may include multiple filtercapacitors coupled in electrical parallel. Furthermore, VSS_(cap) may beequal to VSS_(controller) and to VL₁-VL_(n); for example, all of thesevoltages may equal ground.

As further discussed below, the filter inductor 28 may be omitted if theleakage inductances L_(lk1)-L_(lkn) (discussed below) of the windings 18₁-18 _(n) are sufficient to perform the desired inductive filteringfunction. In some applications, the filter inductor 28 may be omitted toreduce the size and component count of the converter 10.

Each of the windings 18 ₁-18 _(n) of the coupled-inductor assembly 16may be modeled as a self inductance L and a resistance DCR. For purposesof discussion, only the model components of the winding 18 ₁ arediscussed, it being understood that the model components of the otherwindings 18 ₂-18 _(n) are similar, except for possibly their values.

The self inductance L₁ of the winding 18 ₁ may be modeled as twozero-resistance inductances: a magnetic-coupling inductance L_(c1), anda leakage inductance L_(lk1). When a phase current i₁ flows through thewinding 18 ₁, the current generates a magnetic flux. The value of thecoupling inductance L_(C1) is proportional to the amount of this fluxthat is coupled to other windings 18 ₂-18 _(n), and the value of theleakage inductance L_(lk1) is proportional to the amount of theremaining flux, which is not coupled to the other windings 18 ₂-18 _(n).In one embodiment, L_(C1)=L_(C2)= . . . =L_(Cn), and L_(lk1)=L_(lk2)= .. . =L_(lkn), although inequality among the coupling inductances L_(C),the leakage inductances L_(lk), or both L_(C) and L_(lk), iscontemplated. Furthermore, in an embodiment, the respectivemagnetic-coupling coefficients between pairs of coupling inductancesL_(C) are equal (i.e., a current through L_(C1) magnetically inducesrespective equal currents in L_(C2), . . . L_(Cn)), although unequalcoupling coefficients are contemplated.

The resistance DCR₁ is the resistance of the winding 18 ₁ when aconstant voltage V₁ is applied across the winding and causes a constantcurrent I₁ to flow through the winding. That is, DCR₁=V₁/I₁.

The power supply 10 may provide the regulated voltage V_(out) to a load30, such as a microprocessor.

Still referring to FIG. 1, alternate embodiments of the power supply 10are contemplated. Some or all of the phases 12 ₁-12 _(n) may bemagnetically uncoupled from one another. For example, phases 12 ₁ and 12₂ may be formed on a first core and thus may be magnetically coupled,and phases 12 ₃ and 12 ₄ may be formed on a second core separate fromthe first core, and thus may be magnetically coupled to one another butmagnetically uncoupled form the phases 12 ₁ and 12 ₂. Or, a phase 12 maybe magnetically uncoupled from all other phases 12. Furthermore,although described as a multiphase buck converter, the power supply 10may be any other type of multiphase power supply.

FIG. 2 is a schematic diagram of a portion of the power supply 10 ofFIG. 1 including the windings 18 ₁-18 _(n) and an embodiment of thecurrent sensors 14 ₁-14 _(n). For purposes of discussion, it is assumedthat all of the windings 18 ₁ and 18 _(n) are magnetically coupled toone another, and that the filter inductor 28 is omitted from the supply10. For brevity, only the sensor 14 ₁ is discussed, it being understoodthat the other sensors 14 are similar except for possibly the values ofthe components that compose the other sensors.

The sensor 14 ₁ includes a capacitor C₁ across which the sense signalI_(FB1) (here a voltage signal) is generated, an optional scalingresistor RC₁ coupled across C₁, and resistors R₁₁-R_(n1), which arerespectively coupled between the nodes INT₁-INT_(n) and C₁.

The resistor R₁₁ couples to C₁ a signal (a current in this embodiment)that represents the portion of the phase current i₁ that the switchingtransistors 22 ₁ and 24 ₁ (FIG. 1) cause to flow through the winding 18₁.

And the resistors R₂₁-R_(n1) each couple to C₁ a respective signal (acurrent in this embodiment) that represents the respective portion of I₁that a respective phase current i₂-i_(n) magnetically induces in thewinding 18 ₁. That is, the resistor R₂₁ couples to C₁ a current that isproportional to the portion of i₁ that the phase current i₂ magneticallyinduces in the winding 18 ₁. Similarly, the resistor R₃₁ couples to C₁ acurrent that is proportional to the portion of i₁ that the phase currenti₃ magnetically induces in the winding 18 ₁, and so on.

C₁ generates from the sum of the signals from R₁₁-R_(n1) the sensevoltage I_(FB1), which has the same phase as i₁ and which has anamplitude that is proportional to the amplitude of i₁.

Therefore, a power-supply controller, such as the controller 20 of FIG.1, may obtain from I_(FB1) an accurate representation of theinstantaneous phase and amplitude of the phase current

In a similar manner, the capacitors C₂-C_(n) respectively generate thesense voltages I_(FB2)-I_(FBn), from which a power-supply controller,such as the controller 20 of FIG. 1, may obtain accurate representationsof the instantaneous phases and amplitudes of the phase currentsi₂-i_(n).

FIG. 3 is a schematic diagram of a two-phase (n=2) version of thepower-supply portion of FIG. 2.

Referring to FIG. 3, an embodiment of a technique for calculating valuesfor R₁₁, R₁₂, R₂₁, R₂₂, C₁, and RC₁ (if present) is presented. Tosimplify the presentation, it is assumed that R₁₁=R₂₂=R₁, R₂₁=R₁₂=R₂,L_(C1)=L_(c2)=L_(C), L_(Llk1)=L_(lk2)=L_(lk), DCR₁=DCR₂=DCR, andRC₁=RC₂=∞ (i.e., RC₁ and RC₂ are omitted) in equations (1)-(16) below.It is, however, understood that the disclosed embodiment may beextrapolated to a more general embodiment of FIGS. 2-3 for R₁₁≠R₂₂,R₂₁≠R₁₂, L_(C1)≠L_(C2), L_(lk1)≠L_(lk2), DCR₁≠DCR₂, RC₁≠RC₂≠∞, and n>2.

Still referring to FIG. 3, the following equations are derived from thegeneral relationship between the currents through and the voltagesacross reverse-coupled inductors—the windings 18 ₁ and 18 ₂ are reversedcoupled when a positive current flowing through the winding 18 ₁ intothe node 11 induces a positive current in the winding 18 ₂ also flowinginto the node 11.

$\begin{matrix}{V_{1} = {{s \cdot \left( {L_{lk} + L_{C}} \right) \cdot i_{1}} - {s \cdot L_{C} \cdot i_{2}} + {{DCR} \cdot i_{1}}}} & (1) \\{V_{2} = {{s \cdot \left( {L_{lk} + L_{C}} \right) \cdot i_{2}} - {s \cdot L_{C} \cdot i_{1}} + {{{DCR} \cdot i_{2}}\mspace{14mu} {and}}}} & (2) \\{i_{2} = \frac{V_{2} + {s \cdot L_{C} \cdot i_{1}}}{{s \cdot \left( {L_{lk} + L_{C}} \right)} + {DCR}}} & (3)\end{matrix}$

where V₁ and V₂ are the voltages at nodes INT₁ and INT₂, respectively.

From equations (1)-(3), one may derive the following equation for

$\begin{matrix}{i_{1} = \frac{{V_{1} \cdot \left\lbrack {{s \cdot \left( {L_{lk} + L_{C}} \right)} + {DCR}} \right\rbrack} + {s \cdot L_{C} \cdot V_{2}}}{\left\lbrack {{s\left( {L_{lk} + L_{C}} \right)} + {DCR}} \right\rbrack^{2} - \left\lbrack {s \cdot L_{C}} \right\rbrack^{2}}} & (4)\end{matrix}$

Furthermore, where R₁₁=R₁ and R₂₁=R₂ are the resistors coupled to thecapacitor C₁, one may derive the following equation for the voltageI_(FB1) across C₁:

$\begin{matrix}{I_{{FB}\; 1} = {{\frac{\frac{R_{1}}{1 + {s \cdot R_{1} \cdot C_{1}}}}{\frac{R_{1}}{1 + {s \cdot R_{1} \cdot C_{1}}} + R_{2\;}} \cdot V_{1}} + {\frac{\frac{R_{2}}{1 + {s \cdot R_{2} \cdot C_{1}}}}{\frac{R_{2}}{1 + {s \cdot R_{2} \cdot C}} + R_{1}} \cdot V_{2}}}} & (5)\end{matrix}$

Because the voltage VDCR₁ across DCR₁ equals i₁ DCR₁, VDCR₁ has the samephase as i₁, and has an amplitude that is proportional (by a factorDCR₁) to the amplitude of as discussed above in conjunction with FIG. 1,these attributes are suitable for I_(FB1).

Unfortunately, DCR₁ is a modeled component, and one does not havephysical access to the voltage VDCR₁ across it.

But, one can set I_(FB1)=VDCR₁=i₁·DCR₁ according to the followingequation, which is derived from equations (4) and (5):

$\begin{matrix}{\frac{{R_{1} \cdot V_{1}} + {R_{2} \cdot V_{2\;}}}{R_{1} + R_{2} + {s \cdot R_{1} \cdot R_{2} \cdot C_{1}}} = {\frac{{V_{1} \cdot \left\lbrack {{s \cdot \left( {L_{lk} + L_{C}} \right)} + {DCR}} \right\rbrack} + {s \cdot L_{C} \cdot V_{2}}}{\left\lbrack {{s\left( {L_{lk} + L_{C}} \right)} + {s \cdot L_{C}} + {DCR}} \right\rbrack \cdot \left\lbrack {{s \cdot L_{lk}} + {DCR}} \right\rbrack} \cdot {DCR}}} & (6)\end{matrix}$

From equation (6), one can derive the following two equations:

$\begin{matrix}{\frac{R_{1} \cdot V_{1}}{R_{1} + R_{2} + {s \cdot R_{1} \cdot R_{2} \cdot C_{1}}} = {\frac{V_{1} \cdot \left\lbrack {{s \cdot \left( {L_{lk} + L_{C}} \right)} + {DCR}} \right\rbrack}{\left\lbrack {{s\left( {L_{lk} + L_{C}} \right)} + {s \cdot L_{C}} + {DCR}} \right\rbrack \cdot \left\lbrack {{s \cdot L_{lk}} + {DCR}} \right\rbrack} \cdot {DCR}}} & (7) \\{\frac{R_{2} \cdot V_{2}}{R_{1} + R_{2} + {s \cdot R_{1} \cdot R_{2} \cdot C_{1}}} = {\frac{s \cdot L_{C} \cdot V_{2}}{\left\lbrack {{s\left( {L_{lk} + L_{C}} \right)} + {s \cdot L_{C}} + {DCR}} \right\rbrack \cdot \left\lbrack {{s \cdot L_{lk}} + {DCR}} \right\rbrack} \cdot {DCR}}} & (8)\end{matrix}$

Referring to FIG. 1, if one assumes that the controller 20 switches thetransistors 22 and 24 at a relatively high frequency, e.g., 100 KHz orhigher (this assumption applies in many applications of multiphase powersupplies), then one may assume that s(L_(lk)+L_(C)) and sL_(lk) are muchgreater than DCR. Applying these assumptions, equations (7) and (8)respectively reduce to the following equations:

$\begin{matrix}{\frac{R_{1} \cdot \left( {1 + {s \cdot \frac{L_{lk}}{DCR}}} \right)}{\left( {R_{1} + R_{2}} \right) \cdot \left( {1 + {s \cdot \frac{R_{1} \cdot R_{2}}{R_{1} + R_{2}} \cdot C}} \right)} = \frac{L_{lk} + L_{C}}{L_{lk} + {2L_{C}}}} & (9) \\{\frac{R_{2} \cdot \left( {1 + {s \cdot \frac{L_{lk}}{DCR}}} \right)}{\left( {R_{1} + R_{2}} \right) \cdot \left( {1 + {s \cdot \frac{R_{1} \cdot R_{2}}{R_{1} + R_{2}} \cdot C}} \right)} = \frac{L_{C}}{L_{lk} + {2L_{C\;}}}} & (10)\end{matrix}$

From equations (9) and (10), one may derive the following designequations for the sensor circuit 14 ₁ of FIG. 3:

$\begin{matrix}{\frac{R_{1}}{R_{1} + R_{2}} = \frac{L_{lk} + L_{C}}{L_{lk} + {2L_{C}}}} & (11) \\{\frac{R_{2}}{R_{1} + R_{2}} = \frac{L_{C}}{L_{lk} + {2L_{C}}}} & (12) \\{\frac{L_{lk}}{DCR} = {\frac{R_{1} \cdot R_{2}}{R_{1} + R_{2}} \cdot C_{1}}} & (13)\end{matrix}$

Therefore, by selecting the components R₁₁=R₁, R₂₁=R₂, andC₁(L_(C1)=L_(C), L_(lk1)=L_(lk), and DCR₁=DCR are assumed to be knownquantities for purposes of this disclosure) of the sensor circuit 14 ₁such that they satisfy the design equations (11)-(13), the results arethat I_(FB1)≈i₁·DCR₁, and therefore, that I_(FB1) has approximately thesame phase as i₁, and has an amplitude that is approximatelyproportional to (i.e., that has approximately the same amplitude profileas) the amplitude of i₁. Furthermore, because at least in someapplications the design equation (12) may be redundant, one may designthe sensor circuit 14 ₁ by selection component values that satisfy onlythe equations (11) and (13).

FIGS. 4A-4D are respective timing diagrams of I_(FB1), i₁, I_(FB2), andi₂ of FIG. 3 for a two phase embodiment of the power-supply 10 of FIG. 1for the following component values, which satisfy the design equations(11)-(13): L_(lki)=L_(lk2)=200 nanohenries (nH), L_(C1)=L_(C2)=500 nH,DOR₁=DCR₂=2 milliohms (mΩ), C₁=C₂=0.01 microfarads (μF), R₁₁=R₂₂=17kiloohms (KΩ), and R₁₂=R₂₁=24 KΩ. Although I_(FB1) and I_(FB2) arevoltages, the timing diagrams of FIGS. 4A and 4C are in units of Amperes(current) because I_(FB1) and I_(FB2) respectively represent the phasecurrents i₁ and i₂. For purposes of plotting only, I_(FB1) and I_(FB2)have been normalized by setting DCR₁=DCR₂=1 such that I_(FB1) has thesame amplitude profile and phase as i₁, and I_(FB2) has the sameamplitude profile and phase as i₂. Of course the power-supply controller20 (FIG. 1) may adjust the amplitude of the I_(FB1) and I_(FB2) withinthe controller by a scale factor other than unity.

Referring again to FIGS. 1-4D, alternate embodiments of the disclosedtechnique for designing the sensor circuits 14 ₁-14 _(n) arecontemplated. For example, equations (1)-(13) may be extrapolated forthe design of the power supply 10 having more than n=2 magneticallycoupled phases 12 ₁ and 12 ₂ (i.e., for n>2). But the equations (1)-(13)may also be suitable for an embodiment of the power supply 10 havingonly pairs of magnetically coupled phases 12, e.g., phase 12 ₁ coupledto phase 12 ₂ only, phase 12 ₃ coupled to phase 12 ₄ only, and so on.Furthermore, one may modify the equations (1)-(13) to cover anembodiment of the power supply 10 where one or more components of thesensor circuit 14 and winding 18 of one phase 12 have different valuesthan the corresponding one or more components of the sensor circuit 14and winding 8 of another phase 12. Moreover, one may modify equations(9)-(13) so that they are not simplified based on the assumption thatthe controller 20 switches the phases 12 at a relatively high frequency.In addition, although the sensor circuits 14 are described as beinguseful to sense the currents through magnetically coupled phases 12, onemay use the sensor circuits 14 or similar sensor circuits to sense thecurrents through magnetically uncoupled phases. Furthermore, thedisclosed technique, or a modified version thereof, may be suitable fordesigning the sensor circuits of a multiphase power supply other than abuck converter. Moreover, although an embodiment of a technique fordesigning the sensor circuit 14, is disclosed the same or a similarembodiment may be used to design the sensor circuit 14 ₂. In addition,although the sensor circuits 14 ₁-14 _(n) are disclosed as each beingcoupled to the intermediate nodes INT₁-INT₂, the sensor circuits may becoupled to other non-output nodes of phases 12 ₁-12 _(n). The outputnode of a phase 12 is the node where all of the phases are coupledtogether, for example the node 11 in FIG. 2 where the filter inductor 28is omitted.

Referring again to FIG. 3, one may wish to include the optional resistorRC₁ in the sensor circuit 14 ₁ to scale the voltage I_(FB1) such thatK₁·I_(FB1)=i₁·DCR₁, and thus I_(FB1)=(i₁·DCR₁)/K₁, where K₁≦1 (K₁=1 whenRC₁ is omitted). When RC₁ is present and n=n, then the design equations(11) and (13) may be respectively modified into the following equations,assuming that the values of L_(c), L_(lk), and DCR are the same for eachwinding 18 ₁-18 _(n) (because the design equation (12) may redundant asdiscussed above, the equation into which one may modify equation (12)when RC₁ is present is omitted for brevity):

$\begin{matrix}{\frac{R_{11}}{{R_{11} + R_{21} + \ldots + R_{n\; 1}}\;} = \frac{L_{lk} + L_{C}}{L_{lk} + {nL}_{C}}} & (14) \\{\frac{L_{lk}}{DCR} = {\frac{R_{11} \cdot R_{21} \cdot \ldots \cdot R_{n\; 1} \cdot {RC}_{1}}{R_{11} + R_{21} + \ldots + R_{{n\; 1}\;}} \cdot C_{1}}} & (15)\end{matrix}$

And K₁ is given by the following equation:

$\begin{matrix}{K_{1} = \frac{\left( {R_{11} + R_{21} + \ldots + R_{n\; 1}} \right) \cdot {RC}_{1}}{{\left( {R_{11} + R_{21} + \ldots + R_{n\; 1}} \right) \cdot {RC}_{1}} + {R_{11} \cdot R_{21} \cdot {\ldots.} \cdot R_{n\; 1}}}} & (16)\end{matrix}$

The modified design equations for the components of the sensor circuits14 ₂-14 _(n) and the equations for the scale factors K₂-K_(n) may berespectively similar to equations (14)-(16). Furthermore, equations(14)-(16) may be modified where L_(c), L_(lk), and DCR are not the samefor each winding 18 ₁-18 _(n).

FIG. 5 is schematic diagram of a portion of a two-phase (n=2) version ofthe power supply 10 of FIG. 1 including the windings 18 ₁ and 18 ₂(which we magnetically coupled) and another embodiment of the sensorcircuits 14 ₁ and 14 ₂. For purposes of discussion, it is assumed thatthe filter inductor 28 is omitted from the power supply 10. For brevity,only the sensor circuit 14 ₁ is discussed, it being understood that theother sensor circuit 14 ₂ is similar except for possibly the values ofthe components that compose the sensor circuit 14 ₂.

The sensor 14 ₁ includes a capacitor C₁ across which the sense signalI_(FB1) (here a voltage signal) is generated, an optional scalingresistor RC₁ across the capacitor C₁, a resistor R₁ coupled to thecapacitor C₁, and a resistor R₁₁, which is coupled between the phaseintermediate node INT₁ and the resistor R₁. The resistors R₁₁ and R₁couple to C₁ a signal (a current in this embodiment) that represents theportion of the phase current i₁ that the switching transistors 22 ₁ and24 ₁ (FIG. 1) cause to flow through the winding 18 ₁.

Similarly, the sensor circuit 14 ₂ includes a capacitor C₂ across whichthe sense signal I_(FB2) (here a voltage signal) is generated, anoptional scaling resistor RC₂ across the capacitor C₂, a resistor R₂coupled to the capacitor C₂, and a resistor R₂₂, which is coupledbetween the phase intermediate node INT₂ and the resistor R₂. Theresistors R₂₂ and R₂ couple to C₂ a signal (a current in thisembodiment) that represents the portion of the phase current i₂ that theswitching transistors 22 ₂ and 24 ₂ (FIG. 1) cause to flow through thewinding 18 ₂.

The sensor circuits 14 ₁ and 14 ₂ also “share” a resistor R₁₂, which iscoupled between the resistors R₁ and R₂ and also between the resistorsR₁₁ and R₂₂. The resistors R₂₂, R₁₂, and R₁ couple to C₁ a signal (acurrent in this embodiment) that represents the portion of the phasecurrent i₁ that the phase current i₂ magnetically induces in the winding18 ₁. That is, the resistors R₂₂, R₁₂, and R₁ couple to C₁ a currentthat is proportional to the portion of i₁ that i₂ magnetically inducesin the winding 18 ₁. Similarly, the resistors R₁₁, R₁₂, and R₂ couple toC₂ a signal (a current in this embodiment) that represents the portionof the phase current i₂ that the phase current i₁ magnetically inducesin the winding 18 ₂.

One may extrapolate the sensor circuit 14 ₁ for use in the power supply10 (FIG. 1) where n>2 by including in the sensor circuit a respectiveresistive network between the node INT_(I) and all the other nodesINT₂-INT_(n), where each resistive network may be similar to the networkof resistors R₁₁, R₁₂, and R₂₂, except possibly for the values of theseresistors. The resistor R₁ would be coupled to the respective nodes ofthese resistive networks corresponding the node between R₁₁ and R₂₂ inFIG. 5. And the resistors corresponding to the resistor R₂ in FIG. 5would be respectively coupled to the nodes corresponding to the nodebetween R₁₂ and R₂₂ in FIG. 5.

One may extrapolate the sensor circuit 14 ₂ for use in the power supply10 (FIG. 1) where n>2 in a similar manner, and the sensor circuits 14₃-14 _(n) may each be similar to the sensor circuits 14 ₁ and 14 ₂,except possibly for the values of the resistors.

Still referring to FIG. 5, in an embodiment one may derive designequations for the sensor circuit 14 ₁ in a manner similar to thatpresented above in conjunction with FIG. 3. Assuming an embodiment ofthe sensor circuit 14 ₁ where L_(c1)=L_(c2)=L_(c),L_(lk1)=L_(lk2)=L_(lk), DCR₁=DCR₂=DCR, R₁₁=R₂₂=R_(A), and R₁₂=R_(B), thedesign equations for such an embodiment are as follows:

$\begin{matrix}{\frac{R_{A}}{R_{A} + R_{B}} = \frac{L_{C}}{L_{lk} + {2L_{C}}}} & (17) \\{\frac{L_{lk}}{DCR} = {R_{1} \cdot C}} & (18) \\{K_{1} = \frac{{RC}_{1}}{R_{1} + {RC}_{1}}} & (19)\end{matrix}$

Referring again to FIGS. 1 and 5, alternate embodiments of the disclosedtechnique for designing the sensor circuits 14 ₁-14 _(n) of FIG. 5 arecontemplated. For example, equations (17)-(19) may be modified for thedesign of the power supply 10 having more than n=2 magnetically coupledphases 12 ₁ and 12 ₂ (i.e., for n>2). But the equations (17)-(19) mayalso be suitable for an embodiment of the power supply 10 having onlypairs of magnetically coupled phases 12, e.g., phase 12 ₁ coupled tophase 12 ₂ only, phase 12 ₃ coupled to phase 12 ₄ only, and so on.Furthermore, one may modify the equations (17)-(19) to cover anembodiment of the power supply 10 where one or more components of thesensor circuit 14 and winding 18 of one phase 12 have different valuesthan the corresponding one or more components of the sensor circuit 14and winding 18 of another phase 12. Moreover, one may modify equations(17)-(19) so that they are not simplified based on the assumption thatthe controller 20 switches the phases 12 at a relatively high frequency.In addition, although the sensor circuits 14 of FIG. 5 are described asbeing useful to sense the currents through magnetically coupled phases12, one may use the sensor circuits 14 or similar sensor circuits tosense the currents through magnetically uncoupled phases. Furthermore,the disclosed technique, or a modified version thereof, may be suitablefor designing the sensor circuits of a multiphase power supply otherthan a buck converter. Moreover, although an embodiment of a techniquefor designing the sensor circuit 14, is disclosed, the same or a similarembodiment may be used to design the sensor circuit 14 ₂. In addition,although the sensor circuits 1404 ₂ are disclosed as each being coupledto the intermediate nodes INT₁-INT₂, the sensor circuits 14 ₁-14 ₂ (and14 ₃-14 _(n) of present) may be coupled to other non-output nodes of thephases 12 ₁-12 ₂ (and 12 ₃-12 _(n) of present).

FIG. 6 is a block diagram of an embodiment of a system 40 (here acomputer system), which may incorporate a multiphase power supply 42(such as the multiphase power supply 10 of FIG. 1) that includes one ormore phase-current sensor circuits that are the same as or that aresimilar to embodiments of one or more of the current sensor circuits 14of FIGS. 2, 3, and 5.

The system 40 includes computer circuitry 44 for performing computerfunctions, such as executing software to perform desired calculationsand tasks. The circuitry 44 typically includes a controller, processor,or one or more other integrated circuits (ICs) 46, and the power supply42, which provides power to the IC(s) 46—these IC(s) compose(s) the loadof the power supply. The power supply 42, or a portion thereof, may bedisposed on the same IC die as one or more of the ICs 46, or may bedisposed on a different IC die.

One or more input devices 48, such as a keyboard or a mouse, are coupledto the computer circuitry 44 and allow an operator (not shown) tomanually input data thereto.

One or more output devices 100 are coupled to the computer circuitry 44to provide to the operator data generated by the computer circuitry.Examples of such output devices 50 include a printer and a video displayunit.

One or more data-storage devices 52 are coupled to the computercircuitry 44 to store data on or retrieve data from external storagemedia (not shown). Examples of the storage devices 52 and thecorresponding storage media include drives that accept hard and floppydisks, tape cassettes, compact disk read-only memories (CD-ROMs), anddigital-versatile disks (DVDs).

From the foregoing it will be appreciated that, although specificembodiments have been described herein for purposes of illustration,various modifications may be made without deviating from the spirit andscope of this disclosure. Furthermore, where an alternative is disclosedfor a particular embodiment, this alternative may also apply to otherembodiments even if not specifically stated.

1. A power supply, comprising: a supply output node configured to carrya regulated output signal; phase paths each having a respectivephase-path output node coupled to the supply output node, each having arespective phase-path non-output node, and each configured to carry arespective phase current, at least two of the phase paths inductivelycoupled to one another; and at least one sensor circuit each having asensor node coupled to the phase-path non-output nodes of the at leasttwo phase paths and configured to generate a sense signal thatrepresents the phase current flowing through a respective one of the atleast two phase paths.
 2. The power supply of claim 1 wherein all of thephase paths are magnetically coupled to one another.
 3. A system,comprising: a power supply, including a supply output node configured tocarry a regulated output signal, phase paths each having a respectivephase-path non-output node, each having a respective phase-path outputnode coupled to the supply output node, and each configured to carry arespective phase current, at least two of the phase paths inductivelycoupled to one another, at least one sensor circuit each having a sensornode coupled to the phase-path non-output nodes of the at least twophase paths and each configured to generate a respective sense signalthat represents the phase current flowing through a respective one ofthe at least two phase paths, phase-path drivers each coupled to aphase-path non-output node of a respective one of the phase paths, and apower-supply controller coupled to the at least one sensor circuit andthe phase-path drivers and configured to regulate the output signal bycontrolling the at least one phase-path driver coupled to the respectiveone of the at least two phase paths in response to the respective sensesignal; and a load coupled to the supply output node of the powersupply.
 4. The power supply of claim 3 wherein the regulated outputsignal includes a regulated output voltage.
 5. A power supply,comprising: a supply output node configured to carry a regulated outputsignal; phase paths each having a respective phase-path output nodecoupled to the supply output node, each having a respective phase-pathnon-output node, and each configured to carry a respective phasecurrent, at least two of the phase paths magnetically coupled to oneanother; and at least one sensor circuit each coupled to the at leasttwo phase paths and each configured to generate a respective sensesignal that represents the phase current flowing through a respectiveone of the at least two phase paths.
 6. A method, comprising: drivingfirst and second inductively coupled power-supply phase paths withrespective first and second driving signals to generate an outputsignal; generating a first sense signal that represents a firstphase-path current flowing through the first power-supply phase path;and regulating the output signal in response to the first sense signal.7. The method of claim 6, further comprising: generating a second sensesignal that represents a second phase-path current flowing through thesecond power-supply phase path; and regulating the output signal inresponse to the second sense signal.
 8. A power supply, comprising: asupply output node configured to carry a regulated output signal; atleast two phase paths each having a respective phase-path output nodecoupled to the supply output node, each having a respective phase-pathnon-output node, and each configured to carry a respective phasecurrent; and at least one sensor circuit each coupled to the phase-pathnon-output nodes of the at least two phase paths and each configured togenerate a respective sense signal that represents the phase currentflowing through a respective one of the at least two phase paths.
 9. Amethod, comprising: generating a first phase-path non-output signal witha first power-supply phase path; generating a second phase-pathnon-output signal with a second power-supply phase path; generating anoutput signal with the first and second power-supply phase paths;generating a first sense signal in response to the first and secondphase-path non-output signals, the first sense signal representing afirst phase-path current flowing through the first power-supply phasepath; and regulating the output signal in response to the first sensesignal.
 10. The method of claim 9, further comprising: generating asecond sense signal in response to the first and second phase-pathnon-output signals, the second sense signal representing a secondphase-path current flowing through the second power-supply phase path;and regulating the output signal in response to the second sense signal.11. A power supply, comprising: an output node configured to provide aregulated output signal; inductively coupled phase paths each configuredto provide a respective phase current to the output node; and a firstsensor circuit configured to generate a first sense signal thatrepresents the phase current flowing through a first one of the phasepaths.
 12. The power supply of claim 11 wherein the first one of thephase paths includes an inductance.
 13. The power supply of claim 12wherein the first sensor circuit includes a capacitance coupled acrossthe inductance of the first one of the phase paths.
 14. The power supplyof claim 13 wherein the first sensor circuit is configured to generatethe first sense signal across the capacitance.
 15. The power supply ofclaim 11 wherein the first sensor circuit includes: an impedance coupledto the first one of the phase paths; and one or more other impedanceseach coupled to the impedance and to a respective other one of the phasepaths.
 16. The power supply of claim 15 wherein the impedance and theone or more other impedances each include a respective resistance. 17.The power supply of claim 13 wherein the first sensor circuit includes:an impedance coupled to the first one of the phase paths and to thecapacitance; and one or more other impedances each coupled to thecapacitance and to a respective other one of the phase paths.
 18. Thepower supply of claim 11, further comprising a second sensor circuitconfigured to generate a second sense signal that represents the phasecurrent flowing through a second one of the phase paths.
 19. The powersupply of claim 11 wherein the first sensor circuit is coupled to thephase paths.
 20. A method, comprising: generating phase currents withrespective magnetically coupled phase paths; and generating a firstsense signal that represents a first one of the phase currents.
 21. Themethod of claim 20 wherein generating the first sense signal includesgenerating the first sense signal in response to signals respectivelygenerated by the phase paths.
 22. The method of claim 20 whereingenerating the first sense signal includes generating the first sensesignal in response to voltages each at a node of a respective one of thephase paths.
 23. The method of claim 20, further comprising generating asecond sense signal that represents a second one of the phase currents.